The immune system functions to protect individuals from infective agents, e.g., bacteria, multi-cellular organisms, and viruses, as well as from cancers. This system includes several types of lymphoid and myeloid cells such as monocytes, macrophages, dendritic cells (DCs), eosinophils, T cells, B cells, and neutrophils. These lymphoid and myeloid cells often produce signaling proteins known as cytokines. The immune response includes inflammation, i.e., the accumulation of immune cells systemically or in a particular location of the body. In response to an infective agent or foreign substance, immune cells secrete cytokines which, in turn, modulate immune cell proliferation, development, differentiation, or migration. An immune response can produce pathological consequences, e.g., when it involves excessive inflammation, as in allergic inflammatory disorders.
TSLP is an immune cytokine that induces dendritic cell-mediated CD4+ T cell responses with a proallogenic phenotype (Gilliet et al., J. Exp. Medicine 197(8): 1059-1063 (2003). TSLP is involved in the initiation of allergic inflammation (Watanabe et al., Nature Immunology 5: 426-434 (2004); Soumelis et al., Nature Immunology 3: 673-680 (2002)).
The TSLPR chain is a member of the hematopoietin receptor family and binds to TSLP with low affinity. A combination of TSLPR and IL-7Ralpha chain results in high-affinity binding and in STATS activation and cell proliferation to TSLP stimulation.
Antibodies are being developed against a number of antigen targets that are involved in immune diseases. The most significant limitation in using antibodies as a therapeutic agent in vivo is the immunogenicity of the antibodies. As most monoclonal antibodies are derived from rodents, repeated use in humans results in the generation of an immune response against the therapeutic antibody. Such an immune response results in a loss of therapeutic efficacy at a minimum and a potential fatal anaphylactic response at a maximum. Initial efforts to reduce the immunogenicity of rodent antibodies involved the production of chimeric antibodies, in which mouse variable regions were fused with human constant regions. Liu et al. (1987) Proc. Natl. Acad. Sci. USA 84:3439-43. However, mice injected with hybrids of human variable regions and mouse constant regions develop a strong anti-antibody response directed against the human variable region, suggesting that the retention of the entire rodent Fv region in such chimeric antibodies may still result in unwanted immunogenicity in patients.
It is generally believed that complementarity determining region (CDR) loops of variable domains comprise the binding site of antibody molecules. Therefore, the grafting of rodent CDR loops onto human frameworks (i.e., humanization) was attempted to further minimize rodent sequences. Jones et al. (1986) Nature 321:522; Verhoeyen et al. (1988) Science 239:1534. However, CDR loop exchanges may not uniformly result in an antibody with the same binding properties as the antibody of origin. Changes in framework residues (FR), residues involved in CDR loop support, in humanized antibodies may also be required to preserve antigen binding affinity. Kabat et al. (1991) J. Immunol. 147:1709. While the use of CDR grafting and framework residue preservation in a number of humanized antibody constructs has been reported, it is difficult to predict if a particular sequence will result in the antibody with the desired binding, and sometimes biological, properties. See, e.g., Queen et al. (1989) Proc. Natl. Acad. Sci. USA 86:10029, Gorman et al. (1991) Proc. Natl. Acad. Sci. USA 88:4181, and Hodgson (1991) Biotechnology (NY) 9:421-5.
The present invention provides an engineered TSLPR antibody and uses thereof to treat inflammatory, and particularly allergic inflammatory, disorders.